Conventionally, bottles, paper containers, metallic cans, etc., have been used as packaging containers for holding foods such as liquid foods. These packaging containers are sealed after predetermined amounts of liquid foods are charged therein, and are then sold.
Of these package containers, bottles are not suitable for sale using vending machines because they are weak against impacts and are easily broken. Although paper containers are suitable for sale using vending machines because they are not broken by impacts, their flexibility is too high. Therefore, when a paper container is opened, it may be deformed so that liquid food held therein flows out from the spout of the container.
In contrast, metallic cans are suitable for sale using vending machines because they are strong against impacts and have a sufficient stiffness.
However, conventional metallic cans have problems that a difficulty exists in crushing thrown-away empty cans, and that laborious work is needed to separately collect aluminum cans and steel cans. Moreover, even when steel cans, aluminum cans, and the like having a reduced wall thickness are used, there is a limit in reducing their weights. Therefore, costs involved in distribution increase.
In the case where liquid foods are sold by a vending machine after being heated therein, metallic cans must be indirectly heated using hot air, because metallic cans cannot be directly heated by dielectric heating. Accordingly, it takes a prolonged time to heat liquid foods to a proper temperature. In addition, due to the poor thermal insulating performance of metallic cans, a metallic can cannot be held by hand immediately after being taken out from a vending machine. Also, liquid food held therein gets cold in a short period of time.
In view of the foregoing problems of conventional packaging containers, it is an object of the present invention to provide a packaging container which can be easily recycled after being thrown away, which allows food to be heated by dielectric heating, and which has an excellent thermal insulating performance. Another object of the present invention is to provide a method for manufacturing the package container as set forth above.